学习资源 https://www.youtube.com/watch?v=Ulp1Kimblg0web
类的继承 class FutureCar : Car{ } override关键字 super掉用父类ide
对象, 类实例化成为一个对象var car = Car()svg
self refers to the object that is being created学习
if testVar != nil{ } if testVar == nil{ }